Not many months after this lofty deliverance, Blanchard took De Lalande up in a balloon—“the dead borne by the dumb.”
Coulomb’s calculation that a man’s pinions should be half a mile long must have been discouraging to those inventors who believed in him; for, granting that such wings could lift a man, who could lift the wings? And at that date the steam engine was only beginning to develop; the petroleum engine was hardly thought of. No wonder that people turned eagerly to the balloon when it finally appeared.
There has been some controversy as to what person first clearly conceived a feasible design for a balloon. The conception was certainly not new to the world in 1783, when Joseph Montgolfier made his classical experiment. Indeed, prior to that date three distinct principles of aërial flotation had been entertained by natural philosophers; first, that a boat could be so formed of heavy material as to ride on the upper surface of the atmosphere, as a metallic vessel floats on the water; second, that a closed hull, comprising a partial, or complete, vacuum, could be made light enough to rise; third, that a bag could be made buoyant by filling it with material lighter than air. Of course, it is now clear to men versed in mathematics that only the light-gas principle is mechanically applicable. But the vacuum principle still has adherents among inventors who are too “practical” to understand, or trust, exact computation; and the first principle, though now discarded by everyone, was plausible enough, even to accomplished scientific men, before the experiments of Torricelli, and his invention of the barometer, made in 1643. It may, therefore, be interesting to notice some of the proposed, or reported, air ships based upon these various principles. The following is from _Mendoza, Viridario, libri III, probl. 47_:
“Any brass vessel full of air, which otherwise would sink, is sustained on the surface of the water, though naturally of much greater specific gravity; consequently a wooden ship, or one of any other material, placed on the summit of an aërial superficies and filled with elementary fire, will be sustained in that position till the gravity of the vessel becomes greater than the sustaining power of the fire it contains.”
